In an automotive powertrain, a stiff junction between an engine block and a connected transmission bellhousing would benefit from a straight vertical wall, such as a “shear wall”, on the sides of the connecting engine oil pan. The need for tool access, however, tends to move the wall surrounding the oil pan bolts inward. To do this, while maximizing oil volume, requires moving the wall outward between the bolts. The result is an accordion shaped or corrugated sidewall that is easily bent, compromising the pan's contribution to powertrain bending stiffness. An improved oil pan is desired having increased structural stiffness in areas adjoining the transmission bellhousing and adjacent portions of the engine block oil pan flange